Study on histopathology of myxosporadiosis caused by Myxobolus rotundus in crucian carp Carassius auratus auratus

The pathological changes of myxosporadiosis naturally infected by Myxobolus rotundus in crucian carp (Carassius auratus auratus) were studied by conventional paraffin section and hematoxylin-eosin staining. Results show that many milky white cysts at different sizes form on the head, gill and skin of the infected crucian carp; the cysts have a typical 3-layer structure: connective tissue, ectoplasm with double membranes and endoplasm with the spores or trophozoites at different developmental stages. Pathological changes are mainly shown as follows: swollen and proliferated branchial filament in the gill; vacuolation of sinusoid-centric cells in the liver; epithelium necrosis in renal tubules and atrophia in renal glomerulus; necrosis of intestine mucous layer and swollen degeneration of intestine muscle layer; abnormal increase of hemosiderin in spleen.